Warm season grasses provide lush green carpets and ornamental borders for a wide range of commercial purposes such as lawns, parks, golf courses, ground covers, and sports fields. These grasses thrive well in warm weather climates and during the warm season of cold weather climes. However, during periods of cold, even of short duration, grasses such as bahiagrass, Bermudagrass, centipedegrass, St. Augustine grass, and zoysiagrass turn brown and often die. Further, under dry winter conditions, these grasses not only turn brownish, their growth is stunted and they tend to go to seed thus destroying their green carpet or ornamental effect. Natural grasses that remain green during cold weather for the most part do not provide the richness and visual beauty of warm season grasses.
Where warm season grasses are planted for warm weather use, attempts are made to hide the withering and browning effects of cold weather. These include overseeding warm grasses with cold season and transitional grasses such as Kentucky bluegrass, tall fescue, and perennial ryegrass to provide a green cover during the cold season. However, if the temperature goes too low, the desired warm season grass requires replanting in the spring. In some cases a green appearance is maintained during the cold season by using green paint to color brown grass or by spreading green pellets to maintain a green color on the ground. In addition to being high maintenance and costly, these solutions do not provide a suitable alternative for the lushness of a warm season grass turf.
Other solutions are to search for natural mutations of the desired grass known as “sports” or to conduct crossbreeding programs and screen for the desired traits including enhanced cold tolerance. However, few varieties of warm season grass produce low temperature tolerant sports, nor is crossbreeding very successful based upon the few commercially available crossbred grasses. The few known crossbreeds that tolerate cold are limited in variety; difficult to propagate over large areas, variable in temperature tolerance and typically must be sown from sod plugs, as other forms of propagation are not commercially available. Further, these grasses have variable abilities to withstand cold weather and are only available in a few out of thousands of varieties of natural grasses.
Therefore, it would be of considerable advantage to engineer warm season turfgrass and ornamental grasses for enhancement of cold tolerance. Further, it would be of considerable advantage to transform turfgrass, fodder plants (or non-plant) species to withstand colder temperatures in their native and adopted climates especially with abrupt changes in local climates.